"Electronically Reprocessed Stereo" and "Duophonic" recordings

Thank you for being so helpful!

I understand your ambivalence - what you say about the Decca Eclipse ruining what is after all a 'perfectly good mono recording' seems to reflect the perception of reprocessed stereo typically taking away from a performance as opposed to adding anything. In cases it may amount to little more than gimmickry.

Examples of better efforts are worth looking out for - I imagine some sound engineers would be rather more proficient than others. I will keep an eye out for the examples you suggest. Strangely enough it was seeing a 'stereo' Callas/De Sabata Tosca in a charity shop which prompted my interest. That copy looked like it had really been through the wars otherwise I would have given it a try.

I rather like the model of restoring old records attempted by Pristine Classical which is to not only remaster a recording so that clicks and pops caused by the medium (e.g. the lp or tape) are removed but also to then use an equaliser and add ambience to the track to overcome limitations in the actual recording of the work e.g. a recording which is too dry sounding or is poorly balanced.

I couldn't attempt any of that given my limited knowledge of using audio software that is why I am so interested in determining if there is any areas left to explore regarding reprocessing mono to stereo which may add a little excitement to old records but which is quite simple to implement. I really rather enjoy playing about with the sound of old live recordings I have collected through the years.

I don't blame you for not knowing specifics regarding what wizardry was involved - information regarding the actual techniques used seem pretty elusive!

Thanks again

All the best

David

Thank you very much for sharing these links I haven't seen either of them before!

"A Review and an Extension of Pseudo-Stereo for Multichannel Electroacoustic Compositions: Simple DIY ideas" describes how:

"Most impressive and efficient pseudo-stereo is obtained with the spatial distribution of frequencies. In Fig. 1, this was obtained by sending the low frequencies to the left channel and the high frequencies to the right channel with a smooth transition"

This appears to be consistent with what NiklausVogel associates with electronically reprocessed music (and he has significantly more experience of such recordings than I based on his interesting post re the Beecham Boheme)- “some panning of higher to lower frequencies” being evident suggests that the technique described in the Review is indeed part of the technique used by record labels in the 70s and 80s. 

However, NiklausVogel also picks up on the process “adding reverberation”. This is interesting because it suggests that, as well as distributing the frequencies, part of the technique used in the past was possibly to use delays, described in the article as belonging to:
"The second class of methods, less common and less effective, [relying] on space-dependent distribution of very short time-delays (we are not speaking of echoes) and phase distortions of the monophonic signal"  

I have not had much opportunity to read through the articles yet but already a picture is forming based on NiklausVogel’s comments and the sites generously highlighted by SpiderJon which suggests that it may well be possible to discern what techniques were used back in the 70s and 80s quite closely (resembling as they do elements found in "A Review and an Extension of Pseudo-Stereo for Multichannel Electroacoustic Compositions: Simple DIY ideas".) The simplicity of the said effects are encouraging - amateurs could to try out these techniques for themselves using audio software which is available free or very cheaply.

Thank you both for your contributions!

David